How Bitcoin Lets You Spy on Careless Companies

Ringing up a Bitcoin transaction at San Francisco’s Buyer’s Best Friend. Photo: Ariel Zambelich/Wired When Foodler jumped on the Bitcoin bandwagon a few months ago, it seemed like an interesting way to drum up new business. But it turns out that, for some, Bitcoin business can come with an unexpected pricetag: privacy. Since April, the Boston-based online restaurant ordering service, has accepted payments in the world’s hottest digital currency, and sales have grown nicely. Foodler is now doing about $15,000 in Bitcoin food orders per month. This is convenient for customers, and with Bitcoin, the company doesn’t have to fork over the payment-processing fees that come with credit card sales. But there’s a downside: If Foodler isn’t careful, Bitcoin could give competitors a way to spy on its business. To be sure, Bitcoin makes it possible for people to exchange money without...